Fuse unit



Aug- 26, 1947- I A. H. PowELl. 2,426,468

FUSE UNIT Filed Dec. 8, 1943 2 Sheets-Sheet l H Fig. a. .5 'a m7/ s 'f fw al 3 s 34 3L' ,4a 4f l 4 i 31a Inventor: Alr'ic H. Powell,

b F5/W69' 's His Ahum.

Aug. 26, 1947.v

A. H. POWELL 2,426,468

FUSE UNIT Filed Dec. s. 1943 2 sheets-sheet 2 loar I-lis5 Atbornd.

Patented Aug. V26, 1947 FUSE UNIT Alric H. Powell, Yeadon, Pa., assignor to General Electric Company, a corporation of New York Application December 8, 1943, Serial No. 513,391

(Cl. 20G-121) 1s claims. 1

'space required therefor to 'a minimum and to provide a fuse unit which has a dead front so that there is no danger to operators at any time. In my copending application Serial No. 463,752, led October 29, 1942, on which Letters Patent 2,386,060 was granted October 2, 1945, there is disclosed and claimed a new and improved fuse unit which has numerous advantages over the conventional fuse units used heretofore. This fuse unit accommodates cartridge fuses of the type in which the cylindrical ferrules provide the contacts for the cartridge fuse. As a general rule cartridge fuses having current ratings of more than 60 amperes are provided with bladetype contacts.

It is an object of my invention to provide for cartridge fuses having blade-type contacts, a fuse unit which is attractive in appearance, requires less panel space than conventional fuse units used heretofore, and which eliminates the requirement of a fuse block and furthermore provides a dead front construction.

It is another object of my invention to provide an indicating type fuse unit for cartridge fuses of the blade contact type which is relatively inexpensive `and which improves the interrupting capacity of the fuses used therewith.

Still another object of my invention is to, provide a fuse unit for cartridge fuses having blade type contacts in which'the fuse is moved longitudinally into position merely by rotating a portion of the fuse unit.

Further objects and advantages of my invention will become apparent as the following description proceeds, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of my invention, reference may be had to the accompanying drawings in which Fig. l is a front view of a portion of a vertically mounted electric panel or switchboard upon which the fuse unit of my invention is mounted; Fig. 2 is a schematic diagram illustrating the electric circuit of the fuse unit of my invention; Fig. 3 is a sectional view of the complete fuse unit with the fuse in place, although with a certain portion thereof broken away; Fig. 4 is a sectional view through the casing of the fuse unit of my invention taken on line 4-4 of Fig. 3; Fig. 5 is a View of a portion ofthe fuse unit of Fig. 3 with the cover over the indicating lamp removed; Fig. 6 is a view looking into a portion of the base of the fuse unit of my invention with the cartridge fuse removed therefrom; Fig. '7 is a view taken on line 'I-I of Fig. 3 with the cartridge fuse and contacts therefor shown in full; Fig. 8 is a sectional view similar to Fig. 3 of a modification of the fuse unit of my invention; Fig. 9 is a sectional view taken on line 9-9 of Fig. 8; Fig. 10 is a View partly in section similar to Fig. 3 of still another modification of the fuse unit of my invention; Fig, 11 is a sectional view illustrating a further modification of my invention, and Fig. 12 is a perspective View of a portion of the fuse device shown in Fig. 11.

Referring now to Fig. 1 of the drawings, there is illustrated a portion of a vertically mounted electric panel or switchboard I2 having an opening I3 therein through which protrudes a removable insulating member I4 which forms a part of the dead front fuse unit of my invention. This fuse unit is suitably bolted to the panel as by means of bolts I5, also shown in Fig. 4. It will be obvious from Fig. 1 that the fuse unit of my invention which is usually mounted on a vertical panel, has a very pleasing appearance from the front of the panel and as will become apparent from the following description, requires a relatively small amount of panel space.

In the schematic diagram of Fig. 2 of the drawings there is illustrated the electrical circuit of the fuse unit of my invention. The corresponding parts of Fig. 2 are designated by the same reference numerals as in Figs. 1-7 of the drawings. The electrical fuse unit generally indicated as I6 includes a cartridge fuse I'I,'hav ing blade contacts I8 and I9, respectively. The blade contact I8 is electrically connected to terminal 20 of the fuse unit, while blade contact I9 of fuse I'I is electrically connected to the terminal 2| of the fuse unit. The terminals 2|] and '2| have associated therewith suitable female type contacts 22 and 23, respectively, which will be described in greater detail hereinafter. A conductor 24 interconnects the terminal 20 of the fuse unit I6 and the blade contact I8 of the fuse I1 which terminates in a female type contact 25, identical with contacts 22 and 23, forv engaging the blade contact I8. In order to indicate the operating condition of' the fuse I'I an indicating 3 circuit is connected in parallel therewith which comprises a lamp schematically indicated at 26` serially connected with a resistor 21. Suitable conductors 28. 29, 30 and 30 complete the in. dicating circuit and also provide the means for connecting it across the contacts of the fuse I1.

The general arrangement o! the indicating circuit oi' Fig. 2 is well known. The resistor 21 provides suillcient impedance to limit the current ilowing through the indicating circuit when the voltage across this circuit rises upon rupture or blowing of the fuse I1. The lamp 26 is lighted whenever the fuse I'I is ruptured or blown to indicate to the operator that the replacement o1' cartridge fuse I1 is necessary. My invention is particularly concerned with the fuse unit to be described hereinafter which incorporates the general features of the indicating circuit schematically shown in Fig. 2, although certain portions of Fig. 2 have been illustrated in the preferredform embodying my invention.

'I'he fuse unit I6 embodying my invention as shown in Figs. 3 to '7, comprises a base 3| of insulating material which comprises two separate parts 3 Ia and 3|b in order to facilitate assembly of thecontacts and connections contained therein. Each of the parts 3Ia and 3|b of the insulating base 3| is provided with three ears 32, best shown in Figs. 6 and 7, containing openings 33. These ears and openings are designated by the appropriate letter a or b to indicate whether they are a part of portion 3Ia or 3|b. By means of bolts indicated in Figs. 1 and 4 passing through the openings 33, specically designated with the letter a or b to indicate whether the openings are in the portions 3 Ia or 3|b, in base 3| the base may be suitably bolted or fastened to a panel such as I2, having opening I3 therein. The .base 3| would generally be mounted at the back of a vertical panel, such as I2, preferably formed of metal. The opening I3 in the panel would then cooperate with a recess 34 formed in the insulating base 3|, this recess being specifically contained in the portion 3Ia of the base 3|.

' At the end of insulating base 3|, remote from recess 34 there are provided a pair of terminals 20 and 2 Ias indicated in Fig. 2, the terminal 20 entering the base at one side thereof, while the terminal 2| enters the base at thel other side thereof as viewed in Fig. 3. These terminals 20 and 2|, respectively, terminate in spring-blased female type contacts 22 and 23. Each of these spring-biased contacts is identical and comprises a pair of punched parts 35 and 36 which are held together by rivets 31 and springs 38. The part 36 includes bent portions 36 to provide a predeter-4 mined separation between contacting parts 35 and 36. The parts l35 are suitably fastened, as by welding, to terminals 2|) and 2 I, respectively. The spring-biased contact 23 is preferably mounted 'at the bottom of a deep recess 33 in the portion 3|b of base 3| which accommodates a large part of the body of fuse I1, while the contact 22 is mounted considerably above the contact 23 in a recess .40 closely adjacent the portion 3Ia of base 3|. The portion 3Ibof base, 3| is provided with openings 4I adjacent contact 22. the purpose of which Will become apparent as the following description proceeds. Terminals 20 and 2| are suitably threaded so that they may be provided with lock4 Washers 42 and nuts 43, both i'or holding them in position in insulating base 3| as well as to enable` external electrical connections to be made therewith which will be obvious from Figs. 2 and 3. Openings such as 44 inthe lowermost 4 v part of the portion 3|b of base l3|,as vieweddn Fig. 4, are provided to permit ventilation offithe recess 33.

The portion 3Ia of insulating base 3|, also formed of insulating material, is a more or less cup-shaped element including a iloor 3| 'a which forms the bottom of the circular recess 34 into which removable insulating member |4"may be inserted. The surfaces o! the cylindrical walls oi' the recess are threaded as indicated at 45 to engage cooperating threads 4l on removable insulating member I4. The door 3|'a of insulating portion 3Ia is provided with an opening 4l best shown in Fig. '1, which is of a size to permit the fuse I1 to move freely therethrough. Since cartridge fuses of the type such as I1 are usually provided with screws or rivet heads 43 to hold the ferrule such as 43 to the fuse body, the opening 41 is provided with ear-like extensions 41' which will permit the fuse with the rivet or screw heads 43 to pass through opening 41 in a predetermined position. As a matter of fact, the ear-like extensions 41 serve as a guiding means to guide the fuse I1 in its longitudinal movement while being inserted in insulating base 3|. In order to further guide the fuse while being inserted or removed a plurality of projections 50, best shown in Figs. 3 and 7. are provided which extend into the recess 39 and preferably are integrally termed with the iloor 3|'a of the portion 3Ia oi' base 3|. These projections or extensions 50 will guide the fuse I1 in its longitudinal movement and prevent rotation thereof by engaging the rivet or-screw heads 45 in the same manner that the ear-like extensions 41 of opening 41 guide the fuse. The floor 3|'a is also provided with a rectangular opening 5| through which the conductor 24 extends when it engages the contact 22. As soon as the conductor 24 enters opening 5| then the fuse Will be properly guided in its longitudinal movement. However, duringl the time that the fuse is moved from its removed position until the conductor 24 is inserted into opening 5I the ear'- like extensions 41' of opening 41 and the projections 50 in cooperation with the rivet or screw heads 43 of the fuse I1 maintain the fuse in a predetermined non-rotating position during its longitudinal movement into recess 39.

In order to position portion 3Ia and portion 3|b of base3l during the assembly process of the fuse unit of my invention, the adjacent surfaces of these insulating portions are provided with cooperating interlocking members. As shown, the portion 3|b is provided with a rectangular shaped ridge or extension 52 (Fig. 6) which is adapted to fit into a rectangular recess 53 (Fig. 7) in insulating portion 3Ia of base 3|.

In order that the indicating circuit for the fuse unit may be connected to terminal 2| in recess 33, a, ribbon-like conductor 23 is provided which is connected to terminal 2| as indicated at 54. 'This ribbon-like conductor 28 extends to the edge of recess 33 and is suitably fastened as by screw 55 to the surface of insulating portion 3|b which is adapted to be mounted adjacent the door 3|'a of portion 3Ia of base 3|. Also extending from this surface of portion 3Ib which is mounted adjacent the floor 3|'a of insulating portion 3| a, is a projection 56 formed integrally with the portion 3|b. 'I'his projection 56 is in the form of an inclined plane, as best shown in Fig. 3, and is of somewhat circular configuration as indicated in Fig. 6. Aresilient conducting member 28 is mounted along the top edge of projection 56 so that contact with conductor 29 may be made when removable insulating member I4 is -fully inserted in recess 34. When the insulating member I4 is removed from recess 34 the resilient conducting member 28', which is held in place by screw 55 l and electrically connected to conductor 28, raises up from projection 56 thereby providing a contact wipe with conductor 29 as insulating member I4 is inserted fully in recess 3,4. The floor 3Ia of insulating portion 3Ia of base 3l is provided with a narrow curved opening 51, best shown in Fig; .7, into which projection 56 extends. Projection 56 is sufficiently long so that resilient conducting member 28' extends into recess 34 so as to be electrically engaged by conductor 29, to be described hereinafter. Conductor 28 provides a contacting surface equal to about one-eighth of the circumference of insulating member I4 to insure contact with conductor 29.

,In addition to the insulating base and associated terminals described thus far which serve the same function as the fuse block and terminals and the like of the prior art arrangements', my new and improved fuse unit I6 includes the removable insulating member I4 which is generally cylindrical in construction and provided with the threads 46 for threadedly engaging the threads 45 in recess 34. Removable insulating member I4 includes a rst fuse-receiving chamber 58 therein and a second chamber 59 spaced from the rst chamber 58 for housing the resistor 21 and the lamp 26, described above. Mounted within the fuse-receiving chamber 58 is conductor 24, rdescribed above, which is preferably an L-shaped punching having an integral interlock extension 60. The spring-biased contact 25, which may be identical with contacts 22 and 23, is preferably fastened to the L-shaped conductor 24 remote from the portion of conductor 24 which engages contact 22. Preferably the conductor 24 is provided with an integral extension 6I similar to the integral interlocking extension 60, which forms one part of the contact 25 similar to the portions 35 of contacts 22 and 23. The portion 36 of contact 25 is identical with the portion of contacts 22 and 23 marked with the same reference numerals. L-shaped conductor 24 is rotatably mounted within fuse-receiving chamber 58 by a suitable bolt 62, having a shoulder 63 thereon. This bolt passes through an opening 64 in the wall of removable insulating member I4 between the fusereceiving chamber 58 and the second chamber 59. A hexagonal nut 65 mounted in a hexagonal recess 66 in chamber 59 completes the means for holding L-shaped conductor in fuse-receiving chamber 58. 'L-shaped conductor 24 is rotatable about the enlarged portion of bolt 62 formed by virtue of shoulderv 63.

The second, or lamp-receiving chamber 59, is accessible through the removal of a cover 61 which is secured to the end of insulating member I4 opposite the threaded portion thereof. The cover 61 includes an opening 68` therein through which lamp 26 is readily discernible. One terminal of the lamp 26 is connected through conductor 30 to bolt 62 whereby Lit is electrically connected toL-Shaped conductor 24 and consequently to contact 25 which engages the blade contact I8 of fuse I1.

In order to properly position lamp 26 in chamber 59 insulating member I4 is provided with a raised portion 69 (see Fig. 5) extending into chamber 59 which defines a suitable recess 10 of such a size as to accommodate indicating lamp 26. Indicating lamp 26 is preferably a glow lamp of the type containing a mixture of inert gases,

such as a neon lamp or the like. Resistor 21 is preferably mounted adjacent the raised portion 69 and has one end thereof electrically connected with the other terminal of the lamp, as by conductor 3|, while the other terminal of resistor 21 is connected to a screw 1I suitably threaded in the Wall between chambers 58 and 59, best shown `in Fig. 5. Connected to screw 1I is a flat conducting ribboni29 which is accommodated in an undercut recess 12 extending along the Wall of chamber 56. This conductor passes through an opening 13 in the wall between chambers, 58 and 59 and extends for the full length of the fuse receiving chamber 58 through recess 12. The end of conductor 29 remote from screw 1I is bent at right angles 'as indicated at 29 in Fig. 7 so as to extend over the edge of cylindrical insulating member I4 adjacent the threaded end. With' this arrangement, when removable insulating member I4 is threadedly engaged with the recess 34 in |base 3| the end 29 of conductor 29 electrically engages with the spring-like conductor 28 thereby connecting the indicating circuit to the blade contact I9 of fuse I1.

When removable insulating member I4 is removed from recess 34 a cartridge fuse I1 having enters recess 5I.

.chamber 5-8.

blade contacts I8 and I9 may be inserted in fusereceiving chamber 58 so that blade contact I8 is engaged by cooperating spring-biased contact 25. When the blade contact I3 is fully engaged with the cooperating contact 25, as indicated inFig. 3, the interlocking projection 60 of conductor 24 engages with the rivet or screw head 48 of fuse I1 so as to prevent the fuse I1 from being readily removed from fuse-receiving chamber 58 when in engagement with contact 25. With this construction removal of the insulating member I4 will insure that cartridge fuse I1 is also removed and remains within fuse-receiving The removable insulating member I4 with the cartridge fuse held therein by virtue of projection 69 is inserted in the recess 34 of base 3I so that the fuse I1 extends into the recess 39. During this longitudinal movement of the fuse into recess 39 the ear-shaped extensions 41' of opening 41 and the projections 5U guide the longitudinal movement until the conductor 24 The fuse may then be inserted into its conducting position so that blade contact I9 is inserted in contact 23 and conductor 24 is inserted in contact 22 by merelynrotating member I4 so that threads 46 engage cooperating threads 45. This rotation of member I4 causes longitudinal movement of fuse I1 and conductor I 24 without corresponding rotation 'of fuse I1. When the removable member I4 is fully inserted in recess 34 not only is fuse I1 connected across terminals 2U and 2|, but the .indicating circuit in parallel with fuse I1 is also completed between conductor 28 and conductor 29. As long as the fuse I1 is in good current conducting condition substantially no potential will be impressed across the parallel indicating circuit including lamp 26 and resistor 21 so that lamp 26 will not be lighted. I

As soon as the fusible element of fuse I1 is ruptured the potential across the indicating circuit is increased and lamp 26 is lighted. The lamp is visible through opening 68 so that the operator is apprised of the fact that a new fuse is required. Whenever it is desired to open the circuit, insulating member I4 is rotated and by virtue of the threaded arrangement fuse I1 is moved longitudinally to break the circuit between contact 22 and conductor 24 and between contact 23 and blade contact I9. As indicated in the drawings, the circuit is preferably broken at contact 22 and terruption, the openings 4| in cooperation withthe openings 44 provide ventilation for the fuse unit during normal operation.

With the arrangement described above, it is obvious that a dead front construction is provided similar to the arrangement in my copending application so that there is no danger to an operator that contact with a live circuit can be be made. The fuse unit of my invention accommodates cartridge fuses having blade contacts which may be moved longitudinally into andcut of position merely by rotating a portion of the fuse unit. The construction of the fuse unit furthermore permits the operator to be aware at all times of the condition of the fuse. By virtue of the fact that the fuse I1 is completely housed in my fuse unit I8, the interrupting capacity thereof is considerably increased due to the smothering action of the housing. A fuse, according to some standards, is considered to satisfactorily interrupt a circuit if it is not blown apart in this process and furthermore does not cause inflammable material closely' adjacent thereto, to ignite. It is obvious that with my improved arrangement therefor the interrupting capacity of the fuse units according to these standards is greatly increased with less danger to an operator due to flying fuse parts. The fuse may also be replaced without any danger to the operator merely by unscrewing insulating member I4 which then entirely disconnects the fuse from the associated electric circuit. In addition to the advantages enumerated above, my new and improved fuse unit presents a pleasing appearance on a control panel or switchboard as contrasted with the conventional fuse unit used heretofore and not only requires considerably less panel space, as was mentioned above, but actually saves material.

In Fig. 8 there is illustrated a modification of my invention in which the fuse unit generally 'indicated at 15 also accommodates a fuse I1 having blade type contacts I8 and I9. The corresponding parts of Fig. 8 are designated by the. same reference numerals as in Figs. 1 and 7.

This fuse unit 1'5 is also adapted to be mounted on a vertical panel 16 having an opening 11 therein. An insulating base 18, which may be formed of one part if desired, is preferably illustrated as being formed of two parts to facilitate assembly of the contacts and terminals associated therewith. The terminal 2| mounted near the bottom of the recess 19 in base 18 is electrically connected to a resilient contact 80 best shown in Fig. 9. This resilient contact comprises a resilient U-shaped member having one end of the U suitably connected to terminal 2|, as by welding or the like. The other end of the U is engaged by a spring 8| which tends to bias the U towards the closed position. Good electrical contact with the blade type contact I9 and 'contact 80 may be made by inserting the blade type contact I9 so as to assume the dotted position indicated in Fig. 9 and then rotating it in a counterclockwise direction to the position shown in full in Fig. 9 to spread the U-shaped contact 88 apart against the bias of spring 8|. Near the upper end of recess 19 in base 18 there is provided a resilient contact 82 which is adapted to be connected to the other terminal 28 of the fuse unit (not shown).

. Fuse unit 1-5 also includes a removable insulating member 83 including a fuse-receiving chamber 84 and a second chamber 85 similar to the chamber 58 of Fig. 3 for accommodating the indicating lamp 28, etc. A conducting member 88 is rigidly supported within fuse-receiving chamber 84 as by means of a bolt 81. This conducting member has integrally or otherwise suitably fastened thereto a'contact 25 which may be identical with the contact designated by the same `reference numeral in Fig. 3. This contact is adapted to receive the blade contact I8 of fuse I1. The removable insulating member 83 is generally cylindrical in construction with the chamber 84 extending to one end thereof. In order to hold the insulating member 83 in position relative to base 18 itis provided with lugs 88 which are adapted to be inserted in grooves l89 longitudinally formed'in base 18. When the insulating member is longitudinally inserted into the recess formed in base 18 its longitudinal movement is guided by lugs 88 moving in grooves 89. When the vinsulating member 83 is fully inserted in base 18 as indicated in Fig. 8, the lugs 88 move clear of grooves 89 so that insulating member 83 may be rotated not only to lock insulating member 83 into position with respect to base 18, but also to move blade contact I9 from the do-tted position of Fig. 9 to the full position of Fig. 9 to insure good contact between contacts I9 and 80. At the same time conductor 86 is forced into good electrical ccntact with contacting member 82. Although the indicating circuit is not fully disclosed in Fig, 8, it will be understood that it may be very similar to the arrangements disclosed in Figs. 1 to 7. With the arrangement disclosed in Figs. 8 and 9, the removable unit 83 with the fuse I1 inserted in the fuse-receiving chamber 84 is moved longitudinally in position into recess 19 of base 18. By rotating the member 83 slightly in the counterclockwise'directi'on after complete insertion the electrical circuit is completed and a dead front construction similar to that described above is provided.

In Fig. 10 there is disclosed still another modification of myi'nvention in which the fuse unit 90 comprises an insulating base 9| suitably fastened to the back of the vertical panel 92 which is provided with an opening 93 therein cooperating with a recess 94 in base 9|. The terminals of the fuse unitA which arek very similar to the terminals of Fig. 3 have been designated by the same reference numerals, as are also the spring biased contacts associated therewith. The fuse unit -99 also includes a removable member 95 which is very similar to the member 83 of Fig. 8 including a fuse-receiving chamber 96 within which is mounted a conductor 91 extending longitudinally of the chamber 96. This conductor is electrically connected to a contact 25 for engaging the blade contact I8 of fuse I1. With the construction shown in Fig. 10, the removable unit 95 havl ing the fuse I1 mounted therein is inserted in the recess in base 9| so that the fuse I1 is longitudinally moved into position. No rotation of the removable member whatever is required at any time. To hold removable member 95 in position relative to base 9| there is provided a locking member. 98 which is annular in shape so as to fit around removable unit 95. This annular member is provided with lugs 99 adapted to-cooperate with grooves |09 very'similar to the grooves 89 of Fig. 8. The annular locking member 98 is rotated when in the position indicated in Fig. 10 so that the lugs 99 engage shoulders in base 9| to hold removable unit 95 in position. Removable unit 95 is provided with a circumferential extension so that it may be engaged by locking member 08 in order that the latter may properly perform its locking function. The indicating cir.. cuit for lamp 26 is not shown but it should be understood that it may be very similar to the arrangement disclosed in Figs. 1 to '7.y

It may be desirable to provide means for bringing the light from the lamp 26 outside the cap of the fuse unit to make it more readily visible from all angles. To this end I have indicated in Fig. 11 the cap 61 of the fuse unit shown in Figs. 1 to 7, which is provided with a transparent light transmitting insert |03 which will nt into the opening -68 in the cap. It will be understood that this transparent insert |03 preferably formed of plastic or glass, best shown in Fig. 12 may be employed just as well with the fuse unit l5 of Figs. 8 and 9 or with the fuse unit 90 of Fig. 10 as with the fuse unit I6 of Figs. 1 to 7.

This insert |03 has an enlargement |04 for engaging a shoulder associated with opening. 68' in cap 61. Insert |03 also has a concave groove |05 in the bottom thereof into which lamp 26, which is shown in dotted lines in Fig.,11, may iit to hold insert |03 in place. Insert |03 is also provided with lugs |06 and |01. To prevent rotation of lnsert |03 lug |06 lits into a notch |08 formed in cap 6l. Lug |01 also fits into a cooperating notch, not shown.

It should be understood that the expression cartridge fuse as used in this specification and the claims annexed thereto includes any form of fuse enclosed in a tubular shell.

While I have shown and described certain particular embodiments of my invention, I do not desire my invention to be limited to the constructions shown and described for it will, of course, be obvious that changes may be made without departing from my invention. I therefore aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new. and desire to secure by Letters Patent oi the United States, is: A

l rupture 0f said cartridge fuse, means defining l. A dead front cartridge fuse holder and indicator for the cartridge fuse held therein comprising in combination a panel board, a base having a recess therein secured to one face of said panel board, a pair of contact terminals leading into said recess in said base, a cartridge fuse retainer for removably retaining the cartridge fuse thereof within the recess of said base and in series with said contact terminals, an indicating circuit including a lamp for indicating rupture of said cartridge fuse, means dening an opening in said retainer so that said lamp at times is visible from the opposite side of said panel board from that to which said base is secured, a light transmitting insert in said opening so that said lamp is visible at all angles from said opposite side of said panel board, and means for connecting said indicating circuit in parallel with said cartridge fuse at least when retained in contact with said Contact terminals.

2. A dead front cartridge fuse holder and indicator for the cartridge fuse held therein comprising in combination a panel board, a base having a recess therein secured to one face of said panel board, a pair of contact terminals leading into said recess in said base, a cartridge an opening in said retainer so that said lamp at times is visible from the opposite side of said panel board from that to which said base is secured, a

light transmitting insert in said opening so that said lamp is visible at all angles from said opposite side of said panel board, a groove in said insert adapted to lt around said lamp, and means for connecting said indicating circuit in parallel with said cartridge fuse at least when retained in contact with said contact terminals.

3. A dead front cartridge fuse helder and indicator for the cartridge fuse held therein comprising in combination a panel board, a base having a recess therein secured to one face of said panel board, a pair of contact terminals leading into said recess in said base, a cartridge fuse retainer for removably retaining the cartridge fuse thereof within the recess of said base and in series with said contact terminals, an indicating circuit including a lamp for indicating rupture of said cartridge fuse, means defining an opening in said retainer so that said lamp at times is visible from the opposite side of said panel board from that to which said block is secured, a light transmitting insert in said opening so that said lamp is visible at all angles from said opposite side of said panel board, a groove in said insert adapted to t around said lamp, cooperating means on said insert and said cartridge fuse retainer to prevent rotation of said insert, and means for connecting said indicating circuit in parallel with said cartridge fuse at least when retained in contact'with said contact terminals. Y

4. A dead front fuse holder and indicator for a cartridge fuse having at least one blade type contact comprising in combination a base having a recess therein, a pair of contact terminals leading into said recess in said base, an insulating member comprising a cartridge fuse retainer for removably retaining the cartridge fuse thereof within the recess of said base and in series with said contact terminals, and means for longitudinally moving said one blade type contact into or out of electrical connection with one of said contact iermnals by merely rotating said insulating mem- 5. A dead front fuse holder and indicator for a cartridge fuse having at least one blade type contact comprising in combination a base having a recess therein, a pair of contact terminals leading into said recess in said base, an insulating member comprising a cartridge fuse retainer for removably retaining the cartridge fuse thereof within the recess of said base and in series with said contact terminals, means for longitudinally moving said one blade type contact into electrical connection with one of said Contact terminals by merely rotating said insulating member, an indicating circuit including a lamp yin said fuse holder for indicating the condition of said cartridge fuse, and means for also connecting said indicating cirsuit in parallel with said cartridge fuse by rotation of said insulating member.

6. A dead front fuse holder and indicator for a cartridge fuse having at least one blade type contact comprising in combination a base having a recess therein, a pair of contact terminals leading intol said recess in said base, an insulating member comprising av cartridge'fuse retainer for removably retaining the cartridge fuse thereof within the recess of said base and in series with said Contact terminals, means for longitudinally moving said one blade typer contact out of electrical connection'with one of said rcontact terminals by merely rotating said insulating member, an indicating circuit including a lamp in said fuse holder adapted to be connected in parallel with said cartridge i'use for indicating tne condition of said cartridge fuse, and means for also opening said indicating circuit by rotation of said insulating member to move said blade type contact out of electrical connection with one oi said contact terminals.

7. A dead iront tuse holder and indicator for .a cartridge fuse having blade type contacts comprising in combination a base having a recess therein, a pair of contact terminals leading into said recess in said base, an insulating member including a fuse receiving chamber adapted to be removably retained within the recess of said base, an L-shaped conductor mounted within said chamber and having a portion thereof extending longitudinally from said chamber, a contact connected to said conductor within said chamber for electrically engaging one of said blade type contacts of said cartridge fuse, means on said conductor for removably holding said cartridge fuse in said chamber in said insulating member while inserting and withdrawing said insulating member with respect to said recess. and means for longitudinally moving said other blade type contact of said cartridge fuse and the portion oi said L-shaped conductor extending from said chamber into and out of electrical connection with said contact terminals by merely rotating said insulating member.

8. A dead front fuse holder and indicator for a cartridge fuse having blade type contacts comprising in combination a base having a recess therein, a pair of contact terminals leading into said recess in said base, an insulating member Y including a fuse receiving chamber adapted to be removably retained within the recess of said base, an L-shaped conductor mounted within said chamber and having a portion thereof extending longitudinally irom said chamber, a contact connected to said conductor within said chamber for electrically engaging one oi said blade type contacts o1' said cartridge fuse, means on said conductor for removably holding said cartridge fuse in said `chamber in said insulating member while inserting and withdrawing said insulating member with respect to said recess, means in said recess for guiding said fuse while inserting or withdrawing said insulating member with respect to said recess, and means for longitudinally moving said other blade type contact of said cartridge fuse and the portion of said L-shaped conductor extending from said chamber into and out oi electrical connection with said contact terminals by merely rotating said insulating member.

9. A dead front fuse holder and indicator for a cartridge fuse having blade type contactscomprising in combination a base having a recess therein, a pair oi contact terminals leading into said recess in said base. an insulating member including a fuse receiving chamber adapted to be removably retained within the recess of said base, an L-shaped conductor mounted within said chamber for relative rotation therewith and having a portion thereof extending longitudinally from said chamber, a contact connected to said conductor within said chamber for electrically engaging one of said blade type contacts o! said cartridge fuse, means on said conductor for removably holding said cartridge fuse in said chamber in said insulating member while inserting and withdrawing said insulating member with removing said other blade type Contact `of said cartridge fuse and the portion of said L-shaped conductorextending from said chamber into and out of electrical connection with said contact terminals by merely rotating said insulating member around said fuse and L-shaped conductor.

10. A dead front fuse holder and indicator for a cartridge fuse having blade type contacts comprising in combination a base having a recess therein, a pair of contact terminals leading into said recess in said base, an insulating member including a fuse receiving chamber adapted to be removably retained within the recess of said base, a conductor mounted within said chamber and having a portion thereof extending longitudinally lfrom said chamber, a contact connected to said conductor within said chamber for electrically engaging one of said bladetype contacts of said cartridge fuse, means on said conductor for removably holding said cartridge fuse in said chamber in said insulating member while inserting and withdrawing Said insulating member with respect to said recess, and means for longitudinally moving said other blade type contact o! said cartridge fuse and the portion of said conductor extending from said chamber into and out of electrical connection with said contact terminals by merely rotating said insulating member.

11. A dead front fuse holder and indicator for a cartridge fuse having blade type contacts comprising in combination a base having a recess therein, a pair of contact terminals leading into said recess in said base, an insulating member including a fuse receiving chamber adapted to be 'threadedly' engaged with cooperating threads in said recess of said base, a conductor mounted within said chamber and having a portion thereof extending longitudinally from said chamber, a contact connected to said conductor within said chamber for electrically engaging one of said blade type contacts of said cartridge fuse, means on said conductor for removably holding said cartridge fuse in said chamber in said insulating member while inserting and withdrawing said insulating member with respect to said recess, and means for longitudinally moving said other blade type contact of said cartridge fuse and the portion of said conductor extending from said chamber into and out of electrical connection with said contact terminals by merely rotating said insulating member.

12. A dead front fuse holder for a fuse comprising a base having a' fuse receiving recess therein, a contact terminal in said recess, an insulating cover for said base arranged for threaded engagement with said base, a fuse having bladelike terminals adapted to be inserted in said recess with one of said blade-like terminals engaging said terminal in said recess, and swivel means relating said fuse to said coverV so that merely screwing said cover to said base causes said one of said blade-like terminals to electrically engage said contact terminal.

13. A dead front fuse holder for a fuse having at least one blade-type contact comprising in combination a base having a recess therein. a contact terminal leading into said recess in said base, an insulating member comprising a fuse retainer for removably retaining a fuse within the recess of said base and in series with said contact terminal, said retainer being rotatably mounted in said insulating member, and means spect to said recess, and means for longitudinally for moving said one blade-type contact rectilinearly into or out of electrical connection with said contact terminal by rotating said insulating member including means for preventing rotation of said retainer during rotation of the insulating member.

14. A dead front fuse holder for a cartridge fuse having at least one blade-type contact comprising invcombination a base having a recess therein, a contact terminal leading into said recess in said base, an insulating member comprising a cartridge fuse retainer for removably retaining a cartridge' fuse within the recessof said base and in series with said contact terminal, said retainer being rotatably mounted in said insulating member, and means for longitudinally 4moving said one blade-type contact into or out of electrical connection with said contact terminal by rotating said insulating member including means for preventing rotation of said retainer during rotation of the insulating member.

15. A dead front fuse holder for a cartridge fuse having at least one blade-type contact comprising in combination a base having a recess therein, a contact terminal leading into said recess in said base comprising a U-shaped spring biased contact, an insulating member comprising a. cartridge fuse retainer for removably retaining the; cartridge fuse thereof within the recessv of said base and in series with said contact terminal,` and means for moving said one blade-type contact into or out of electrical connection with said contact terminals by merely rotating said insulating member.

16. A fuse holder for a fuse comprising a base having a pair of terminals mounted therein, an insulating cover for said base including a recess having a third terminal mounted therein, a fuse having blade-like contacts inserted in said recess 14 with one ci' said contacts in electrical engagement with said third terminaLgand means for relating said cover to said base so that said fuse is connected across said pair of .terminals in said recess.

17. A fuse holder for a fuse comprising a base Y having a pair of terminals mounted therein, an insulating cover for saldbase including a recess having a third terminalfmounted therein, a fuse having blade-like contacts inserted in said recess with one of said contacts in electrical engagement with saidk third terminal, and threaded means for relating said cover to said base so that said fuse is connectedacross said pair of terminals in said recess.

18. A fuse holder for aefuse comprising a base having a pair of terminals mounted therein, an insulating cover for said. base including a recess having a thirdterminal mounted therein, a fuse having blade-like contacts inserted in said recess with one of said contactsxin electrical engagement with said third terminal, and an independent insulating member forrelating saidy cover to said base so that said fuse-is connected across said pair of terminalsin said recess.

ALRIC H`. POWELL.

REFERENCES CITED The followingl references areof record in the le of this, patent:-

UNITED STATES PATENTSv Number Name Date 1,858,157 Lagandro May 10, 1932 2,207,837 Sundt July 16, 1940 1,785,546 Sloane June 24,' 1930 890,928 Clausen Jan. 14; 1902 

